Many aircraft include control surfaces that may be extendable from the leading and/or trailing edges of the aircraft wings. For example, many aircraft are fitted with wing flaps that may be extended from the wing trailing edges to increase the lift capability of the wings during takeoff and landing of the aircraft. Each trailing edge wing flap may be mounted to the wing by a pair of flap track assemblies which may be located near the inboard and outboard ends of each flap. The flap may be coupled to each track assembly by a flap carriage which is movable along a flap track of the track assembly.
The flap carriage may include one or more track roller bearings or roller assemblies that are in rolling contact with the flap track. The track assembly may further include a flap actuation mechanism for extending the flap away from the trailing edge to a desired flap setting and retracting the flap back toward the trailing edge. The flap actuation mechanism may comprise a motor coupled to a suitable drive mechanism such as a ballscrew. The ballscrew may include a drive screw affixed at one end to the motor and at an opposite end to a ball nut attached to the flap carriage. Rotation of the drive screw by the motor causes translation of the ball nut and flap carriage along the drive screw resulting in extension or retraction of the flap depending upon the direction of rotation of the drive screw.
During certain phases of flight, the flaps may be exposed to vibrational loading. For example, during takeoff and landing when the flaps are typically extended, a portion of the engine thrust may impinge upon the flaps causing the flaps to vibrate. Aerodynamic loading on the flaps may also contribute to vibration of the flaps. In addition to thrust impingement and/or aerodynamic loading, mechanical vibrations caused by engine operation and rough runway surfaces may also cause vibration of the flaps. The vibration of the flaps may be transmitted through the flap carriage to the roller assemblies which are supported by the flap track. Each roller assembly includes an outer roller surface which is in rolling contact with a track surface of the flap track. The vibrational motion of the flap causes axial motion of the roller surface which may result in a reduction in the service life of the track surface. In addition, axial motion of the roller surface relative to the track surface can result in an increase in maintenance costs and require repair of the track surface or replacement of the flap track.
Repair of the track surface to extend the operating life of the flap track may require the application of a high-hardness coating to the track surface. Unfortunately, the application of the high-hardness is a relatively expensive process requiring significant labor for removal of the track assembly from the aircraft, disassembly of the flap track from the track assembly, and re-working of the flap track to apply the high-hardness coating. Likewise, replacement of the flap track is also relatively expensive and time-consuming requiring removal of the track assembly, replacement of the damaged flap track with a new flap track and re-installation of the track assembly onto the aircraft. In addition, each of the above-described repair or replacement scenarios can result in significant aircraft downtime.
As can be seen, there exists a need in the art for a roller assembly of a track assembly that minimizes or eliminates axial motion of the outer roller surface relative to the track surface. Additionally, there exists a need in the art for a roller assembly that minimizes or prevents such relative axial motion of the outer roller surface and wherein the roller assembly is of low cost and simple construction.